The psychophysical research proposed in this subproject will examine three types of sensory interactions involving pain -- touch gating, pain gating, and diffuse noxious inhibitory controls (DNIC) -- in normal subjects, and in patients with fibromyalgia (FM) and temporomandibular disorders (TMD). The etiology of these two chronic-pain conditions is obscure, but their symptomatology includes evidence of a centrally mediated enhancement of sensitivity to noxious stimuli. The proposed research explores the possibility that disturbances of pain gate and DNIC contribute to the magnitude of this enhancement, and that touch gate can serve as an index of its severity. Major goals of the research are to analyze the ways in which these sensory interactions vary as a function of clinical status, the extent to which their strengths are statistically related across individuals, and their degree of association with hypervigilance, as indexed by detail of pain report and other measures. Forced-choice measurement of detection and discrimination thresholds will be used to explore impairments of vibrotaction produced by pain (usually attributed to a "touch gate"): These experiments will reveal whether experimental and clinical pain have comparable effects on the touch gate, and whether, in FM as in TMD, frequency discrimination is impaired more than other measures of vibrotaction. Visual analog scaling will be used to examine the effects of vibratory stimulation on pain intensity (pain gating), and the way in which this form of interaction depends on vibration frequency. DNIC will be studied both in the context of its ability to suppress slowly increasing (C-fiber mediated) pain, and to block the temporal summation associated with wind-up.